Hypothyroidism: Introduction

Hypothyroidism is a common disorder that occurs when the thyroid gland is underactive and does not produce enough thyroid hormone. The thyroid gland is located in the front part of the neck, and the hormone it produces is vital to normal metabolism. A lack of thyroid hormone results in a slowing of the body's chemical processes and metabolism. Hypothyroidism may also lead to serious, potentially life-threatening complications.

Hypothyroidism, also called myxedema, hypothyroid or underactive thyroid, is more common in women than in men. It is also more common in people over 50 years of age.

Hypothyroidism can be caused by a variety of diseases and conditions. Most commonly, it is the result of inflammation of the thyroid gland. It can also be caused by viral thyroiditis or a disease called Hashimoto's thyroiditis, an autoimmune disease. In Hashimoto's thyroiditis the body's immune system mistakes healthy thyroid tissue as foreign and potentially dangerous invaders into the body and attacks it. This results in inflammation of the tissue that eventually can destroy the function of the thyroid gland.

Hypothyroidism may also be caused by treatments for hyperthyroidism and some types of medications and radiation treatments. Disorders of the pituitary gland or the hypothalamus can also result in hypothyroidism because these glands control the function of the thyroid gland. Rarely, an infant may also be born without a thyroid gland or with an abnormal one due to a birth defect.

The symptoms of hypothyroidism can vary between individuals and tend to be mild or vague in the early phases of the disorder. Early symptoms frequently include fatigue and weight gain. The most extreme form of hypothyroidism is a life threatening complication called myxedema coma. Symptoms of myxedema coma include shock and unresponsiveness. For more details on symptoms, refer to symptoms of hypothyroidism.

Making a diagnosis of hypothyroidism begins with taking a thorough medical history, including symptoms, and completing a physical examination. The physician or health care provider may feel a smaller or larger than normal thyroid gland in the neck. A blood test is performed to determine levels of thyroid stimulating hormone (TSH) and the thyroid hormone thyroxine. High levels of TSH and low levels of thyroxine indicate that a thyroid gland is underactive.

Other tests may be performed to check for potential complications of hypothyroidism, such as heart disease. These can include blood tests that can reveal hypercholesterolemia, increased liver enzymes, or anemia. A chest X-ray may be done to evaluate the size of the heart.

It is possible that a diagnosis of hypothyroidism can be missed or delayed because the disease may progresses gradually, and early symptoms can be mild or assumed to be associated with other conditions, such as aging or stress. For more information on misdiagnosis, refer to misdiagnosis of hypothyroidism.

Hypothyroidism cannot be cured, and people with the disorder have to take thyroid hormone replacement medication for the rest of their lives. However, this treatment is generally very effective in relieving symptoms. For more information on treatment, refer to treatment of hypothyroidism....more »

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